Paul Decker murders his wife in her Italian villa by drugging her milk and asphyxiating her by gas. He cleverly locks the bedroom from the inside and hides inside a trapdoor in the floor until after the body is discovered by servants. He uses a scuba snorkel connected to tubes on the outside to breathe during the ordeal. Decker's stepdaughter Candy suspects him immediately, especially since no suicide note was found. She also is convinced that he murdered her father years before, but her accusations fall on deaf ears. The ruthless Decker even poisons the family spaniel when the pet takes too great an interest in the mask and realizes he will ultimately have to get rid of Candy too. 说说结局。 在位于海滨的别墅内，保罗·德克尔（皮特·范·埃克 Peter van Eyck 饰）用煤气杀害了自己的妻子，并将房间伪装成自杀现场，而自己则戴上水下呼吸器藏在地板下，制造不在场证明。所有人包括警察在内都认定德克尔夫人死于自杀，但是死者的女儿坎蒂（Mandy Miller 饰）坚称保罗才是真正的凶手。原来保罗并非坎蒂的女儿，在坎蒂8岁时她曾随父亲和保罗出海游玩，却目睹了父亲被对方杀害的经过，在此之后保罗变成了坎蒂的继父。 坎蒂虽然疑窦重重，然而保罗却心思缜密、狡猾非常，几乎不露出任何马脚。为了彻底霸占家产，也为尽快除掉隐患，他开始谋划向坎蒂施以毒手……
